This is a continuation of a project to characterize the ultrasonic properties of myocardial tissue in[unreadable] health and disease and to utilize this knowledge in the development of[unreadable] methods to assess regional myocardial perfusion, function, and viability.[unreadable] They have found in previous work that velocity, backscatter, and attenuation[unreadable] of ultrasound vary substantially with the angle of insonification relative[unreadable] to the local arrangement of fibers in the myocardial walls. This anisotropy[unreadable] has largely been ignored, but is thought to be responsible for the drop out[unreadable] of lateral wall echoes in some views of the heart. It is especially[unreadable] important in tissue characterization where subtle changes in ultrasonic[unreadable] properties caused by disease or other abnormalities must be detected in the[unreadable] face of alterations due to angle of incidence. Contrast echocardiography[unreadable] has the potential for assessment of regional myocardial perfusion, but they[unreadable] have found that anisotropy of backscatter and attenuation confounds these[unreadable] measurements as well. In this competitive renewal they propose to: 1)[unreadable] measure the anisotropy of ultrasonic backscatter, attenuation, and velocity[unreadable] in myocardial tissue and delineate the responsible mechanisms; 2) develop[unreadable] strategies for exploiting the knowledge and overcoming the potential[unreadable] difficulties anisotropy presents in echocardiographic imaging, tissue[unreadable] characterization, and contrast echocardiography; and 3) provide baseline[unreadable] knowledge of the anisotropy of myocardial mechanical and elastic properties[unreadable] to improve understanding of cardiac mechanics in normal and diseased hearts.[unreadable]